1. Field of the Invention
The present invention relates generally to devices, articles, and methods for effecting and enhancing wound closure in tissue. More particularly, the present invention relates to a method and apparatus for heating a sealant material and applying the heated sealant to tissue to close wounds and to join severed vessels.
Most surgical disciplines are concerned with the repair of damaged tissues and vessels. Tissue damage can be the result of direct trauma to the body or as part of a surgical procedure in which there is a separation of normally continuous tissue such as blood vessels. Historically, suturing has been the accepted technique for rejoining severed tissues and closing wounds. To suture a wound, the surgeon manually stitches the surrounding tissue with a surgical needle and suturing thread, and more recently, with a variety of polymeric or metallic staples.
While suturing and stapling techniques are often successful, there are a number of limitations inherent in such mechanical approaches. The practice of suturing or stapling tissue together not only requires significant skill, but is a relatively slow process, particularly when extensive repair is required or when anastomosing tiny biological structures. Even when suturing is properly performed, however, this technique can be less than satisfactory because of the gaps which are left between the stitches and the possibility of progressive structural weakening over time. For example, the gaps leave the wound open to bacteria, producing a risk of infection. In addition, the suture needle or staples puncture the tissue, producing holes through which biological fluid may leak.
In an effort to overcome the difficulties associated with conventional suturing techniques, sutureless repairs using surgical adhesives or glues have been developed. These surgical adhesives adhere to tissue surfaces and form a bond until the tissue heals. For example, one common tissue adhesive is fibrin adhesive or glue typically containing a concentrate of fibrinogen and thrombin. These agents are mixed together to form a clot joining separated tissues, forming a biocompatible bond therebetween. Fibrin adhesive, however, is usually obtained from pooled human plasma and the threat of infection from agents such as Hepatitis "B", HIV virus or others has outweighed the benefits of obtaining commercial quantities of fibrin adhesive. Non-biological materials, such as isobutyl-2-cyanoacrylate, have also been examined as potential surgical adhesives. These materials, however, are generally irritating to tissues, difficult to apply and often fail to form a permanent closure.
In another approach, electrosurgical, cauterization and cryogenic techniques have been developed to reduce the flow of blood in a wound or a surgically-induced incision. Electrosurgical procedures, either monopolar or bipolar, usually operate through the application of very high frequency currents to cut or ablate tissue structures. Cauterization involves using intense heat to sear and seal the open ends of the tissue. This heat can be generated by a variety of different methods, such as resistance heating of a metallic probe. Cryogenic techniques involve applying a cryogenic temperature to freeze the tissue, thereby discontinuing undesired blood flow. These electrosurgical, cauterization and cryogenic techniques, however, may damage or destroy the surrounding tissue leading to longer healing times, infection and scarring. Electrosurgical techniques, particularly monopolar procedures, also create the potential danger that the electric current will flow through undefined paths in the patient's body, thereby increasing the risk of unwanted electrical stimulation to portions of the patient's body.
More recently, lasers have been utilized to controllably generate high intensity optical energy that is absorbed by the damaged tissue. The heat produced by absorption of the optical energy converts biological tissue into a denatured proteinaceous substance which forms a biological glue that closes the wound. Similar to cauterization techniques, however, the high intensity optical energy in this procedure creates a substantial risk of damaging neighboring tissues.
For these and other reasons, it would be desirable to provide procedures for effectively sealing damaged tissue structures, such as torn vessels or open wounds. These procedures should be capable of forming an immediate closure of the damaged tissue to prevent further blood leakage and creating a permanent seal around the wound, while minimizing damage or destruction of surrounding tissue.
2. Description of the Background Art
U.S. Pat. Nos. 4,854,320 and 5,140,984 describe the use of laser emitted optical energy to heat biological tissue to a degree suitable for denaturing the tissue proteins such that the collagenous elements of the tissue form a "biological glue" to seal the tissue. PCT Application WO 94/21324 describes an applicator for introducing a fluent prepolymer liquid onto a wound. The prepolymer is then heated in situ to solidify the prepolymer, thereby creating a bond with the tissue. U.S. Pat. No. 4,034,750 describes a method for electrochemically-linking collagen membranes to the damaged collagen fibrils of an animal body. U.S. Pat. No. 5,156,613, PCT Application WO 92/14513, and copending application Ser. No. 08/231,998, assigned to the assignee of the present invention, describe a method for joining or reconstructing tissue by applying energy to a tissue site in the presence of a collagen filler material. Copending application Ser. No. 08/370,552 describes the use of an inert gas beam energy source for fusing collagen and other materials to tissue for joining or reconstructing the tissue. U.S. Pat. No. 5,071,417 describes the application of laser energy to biological materials to seal anastomoses.